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From: Eric.Bohlman@p1.f778.n115.z1.fidonet.org (Eric Bohlman)
Newsgroups: misc.handicap
Subject: using extended memory
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Date: 3 Oct 90 14:36:45 GMT
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Index Number: 10847

[This is from the Blink Talk Conference]

386-specific memory managers like QEMM or 386-to-the-max have
features for loading TSR's into "high memory" which is defined as
memory between 640K and 1M.  I'm not sure whether they can remap
extended memory (memory above 1M; a system with 1M of memory
usually has 384K starting at the 1M point) into high memory, though
they can map it into expanded memory (in theory, they should be
able to remap extended memory to high memory using the 386 mapping
registers, but I don't know whether they actually implement it).
The problem I see is that JAWS is bigger than 64K, and it's
difficult to find a contiguous area of high memory bigger than
64K.  A0000-AFFFF is sometimes available (especially if you have an
EGA or VGA and don't use graphics mode).  However, some of the
B0000-BFFFF block is always going to be taken up by screen memory,
and C0000-CFFFF will have your hard disk BIOS.  D0000-EFFFF might
be a possibility, whereas F0000-FFFFF is reserved for the system
BIOS.

As Willie pointed out, Vocal-Eyes can run in extended memory with
an XMS driver (HIMEM.SYS).  However, I suspect that it loads into
what's known as the "high memory area" (which is not the same thing
as the "high memory" we were talking about before).  It turns out
that due to a lucky quirk in the way the 80286 and 80386 were
designed, the CPU can access almost all of the first 64K of
extended memory while remaining in real mode (the CPU has to be
running in real mode to use DOS.  In protected mode, the CPU can
access the rest of extended memory, but the interrupt structure and
segmentation aren't compatible with DOS).  Again the problem is
that JAWS is to big to fit in that area.

If you can get a hold of QEMM or 386-to-the-max cheaply, you might
try them and see what they can do, but I wouldn't hold out too many
hopes.

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